Crows

While bicycling in the Turtle Mountains recently I observed a flock of over a couple hundred or so crows perched in some trees. I couldn’t help but think of the movie “The Birds!” I knew better of course, but I was just waiting for them to start attacking.

Crows often get a bad rap. They are often blamed for eating the eggs of chickens, waterfowl, and other birds. That may happen, but depredation by crows is generally not considered a major factor in egg loss. Crows are omnivorous and consume a wide variety of items from frogs and insects to grain and carrion.

But back to the movie “The Birds.” Most of you are probably familiar with the 1963 Hitchcock movie. The movie is set in California where a playgirl pursues a potential boyfriend, and in typical Hitchcock fashion, things get bizarre when “the birds” such as crows and gulls begin to viciously attack city residents.

Perhaps like you, I have wondered how Hitchcock came up with a story like that. Actually, we may know part of the answer. During August of 1961 in Capitola, California many shearwaters (a gull-like bird) were observed flying into buildings and other objects, while others lay dead on lawns and streets. Obviously something pretty strange had happened. The Santa Cruz Sentinel wrote about it, and Hitchcock reportedly requested information from the newspaper about the event to use as “research material for his latest thriller.”

So what caused this ornithological mayhem? Toxic algae may have been involved. Many different algae are known to produce toxins, including neurotoxins. Some of you may be aware of an occasional algae bloom in a dugout, stock pond or other body of water that can cause livestock poisoning. The infamous “red tides” are caused by algae called dinoflagellates.

One of these neurotoxins, domoic acid, can be transferred up the food chain, for example from algae, to minnow, to gull. If the gull were to ingest a large amount of the domoic acid from the minnows, brain damage could occur. This is known to cause unusual behavior resembling suicidal behavior, and may even be fatal.

But don’t worry. “The Birds” is still fiction. Plus there aren’t many algae blooms around here right now!

Chuck Lura

Natural North Dakota is supported by NDSU Central Grasslands Research Extension Center and Minot State University-Bottineau, and by the members of Prairie Public. Thanks to Sunny 101.9 in Bottineau for their recording services.

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